Suicide is a leading cause of death in the United States. Thus, it can rightfully be viewed as a public health problem. Unfortunately, the prevention of suicide has proven to be a difficult task, which is likely due to the fact that much remains unknown. Joiner's (in press) interpersonal-psychological theory of attempted and completed suicide proposes that there are three factors that are both necessary and sufficient for an individual to have the desire and ability to complete suicide: perceived burdensomeness, thwarted belongingness, and the acquired ability to engage in acts of self harm. The proposed project will test portions of the third factor of the theory (i.e., the acquired ability to engage in acts of self harm) by conducting three studies. The first study will explore factors (i.e., previous experience with painful stimuli) that differentiate those who complete suicide from those who attempt suicide. The second study will examine how impulsivity relates to pain tolerance, a factor posited to contribute to the ability to engage in lethal suicidal behavior. The third study will investigate gender differences in mood lability and how these differences facilitate exposure to painful stimuli, thereby conferring additional risk for suicide. [unreadable] [unreadable] [unreadable]